The present invention relates to the measurement and determination of the integrity of test objects such as components of structural material.
In our copending application Ser. No. 438,864, we have proposed a method and device for the determination and detection of cracks in test objects whereby light conducting fibers such as synthetic fibers, glass fibers or quartz fibers are attached to the surface of a test object. Through appropriate coupling techniques light is transmitted into one end of these fibers and the transmission of that light is monitored at the respective other end of each and all of the fibers. Thus, the monitoring process proper relates to monitoring the transmission of light through these fibers. Any crack in the test object will cause the respective fiber or fibers above to crack likewise causing a drastic reduction in light transmission through the respective fiber. This reduction is detected and used as indication for the occurence of a crack. The method particularly is advantaged by the fact that the crack formation is irreversible, particularly as far as the fibers are concerned. Thus, cracks in a component of a structural material may hardly be detectable as such after for example the overload causing the crack has decayed. However, a crack in such a glass fiber reduces the light transmission therethrough even if the bounding surfaces of the crack abut very closely; the transmission characteristic is irreversibly altered and remains permanently available as an indication that indeed a local crack was produced.